In wireless cellular communication system, the system side sends information which is completely the same for all the configuration of terminals in the cell by broadcasting messages, saving wireless resources, and terminals may obtain sufficient access information to set up a wireless connection with network by messages broadcasted by system.
In the third generation mobile communication LTE system, the starting location, the period and gap of the measurement gap are configured by RRC (Radio Resource Control) layer. The terminal finishes the measurement according to the configured measurement period. During the period of measuring the measurement gap, terminals can't communicate with the system side, i.e. during measurement gap, communication stops.
For downlink processing based on the measurement gap, it's only defined that the transmission of downlink data can't conflict with the measurement gap when scheduling data. For uplink feedback, terminals do not give any feedback during measurement gap. When terminals adopt non-adaptive retransmission, the system side continues retransmission according to the result of no feedback from the terminals, i.e. during the period of measuring the measurement gap, it is impossible for terminals to receive data and give feedback, therefore, this may cause an out-of-step between tasks of system side and terminals, meanwhile increasing the resource overhead for scheduling ineffectively, reducing the performance of system.